Start by killing the only enemy in the level - a dog.Pick up the flares in the alcove and jump up to where the water pours out of the wall. Climb higher and jump across towards the railing. Walk around the next corner and then jump grab across to land right on top of the Yellow Plug (Watch out for the invisible door block right next to it). Pick it up and go back up via a running jump with grab. You can pull up to the railing and jump over it.

Climb the ladder in the back to get up to the next level. Walk around and use the plug. Enter the now open door. Go across the room and into the bathroom and pick up the Key on a block in the back corner. There is nothing to do in the other adjacent room. So, go back out, climb the block next to the yellow plug receptacle and climb up to the next level.

Make your way to the block, climb it and do a running jump across to the other side. Then from there jump twice along the East wall to reach the other side and climb up to the roof. Find the Key Hole in the back and use the Key to open the door. Go through and the level ends.